Source-Rock Quality and Thermal Maturity, Palo Duro Basin, Texas: ABSTRACT

Abstract

Measurements of source-rock quality in the Palo Duro and Dalhart basins suggest that fair to very good hydrocarbon source materials are present. Total organic carbon (TOC) was measured in samples taken from a range of depths and stratigraphic intervals, with sampling concentrated in Pennsylvanian and Wolfcampian shales from basin and prodelta facies. TOC content for all samples ranges between 0.008 and 6.866 wt %. Highest TOC content is in Upper Permian (Guadalupian) San Andres dolomite in the southern part of the basin. Pennsylvanian and Wolfcampian basinal shales are fair to very good source rocks on the basis of TOC values of up to 2.4%. Optical properties of organic material in source rocks, especially kerogen and vitrinite reflectance, indicate maximum paleotemperatures. Pennsylvanian and Wolfcampian kerogen is yellow-orange to orange, which indicates slight thermal alteration. Temperatures were probably high enough to begin generation of hydrocarbons from lipid-rich organic material, which is most abundant in the deep-basin shale facies. Palo Duro basin samples have a broad range of vitrinite reflectance values (Ro), but populations with the lowest reflectance probably indicate the true paleotemperatures reached. Vitrinite with higher reflectance may have been reworked from older sediments. The average reflectance in representative Pennsylvanian vitrinite is 0.52%; in Wolfcampian samples the average reflectance is .48%. These values are consistent with the kerogen color and suggest that source rocks in the Palo Duro basin may have begun to generate hydrocarbons. Potential hydrocarbon reservoirs are present in shelf-margin dolomite, fan-delta, and high-constructive delta sandstone. Juxtaposed reservoir facies and source beds delineate possible hydrocarbon fairways. End_of_Article - Last_Page 702------------